The present invention relates to the treatment of toxic waste contaminated sites or spill sites which may contain chemical and/or radioactive compositions that pollute the environment and threaten public health and safety. The sites may contain one or more of various chemical and radioactive compositions, hydrocarbons, e.g., oil spills, and metals. The contaminants present in such sites are wide ranging in both type and concentration levels. They vary from a wide range of organic, chlorinated and inorganic compounds and precious metals and in some cases such compounds may be mixed with radioactive materials ranging from low to intermediate radioactivity levels.
Conventional methods of remediating such waste disposal sites include:
1. Excavation and transportation of contaminated soils to other landfills;
2. Excavation and transportation of contaminated soils to a central offsite treatment plant;
3. Physical containment of the waste site with an impermeable wall which prevents migration of contaminants into the groundwater;
4. In situ treatment of the contaminants by stripping volatile organic compounds therefrom without excavation; and
5. In situ addition of treatment reagents without excavation.
Each of the above methods includes various drawbacks which primarily render them cost ineffective, dangerous to treatment personnel and generally ineffective treatment.
Operations which involve physical transportation of contaminated materials to a different treatment or landfill site clearly involve extra hazards of spill accidents during transport and the natural reluctance of residents in proximity to a landfill to accept additional materials which have been removed from other landfills or contaminated sites.
Those treatment methods which involve physical containment of a waste site with a contaminant barrier wall result in a "bathtub effect" which often creates undesired downward migration or spillover of the contaminants through cracks or porosity of the containment wall. These undesired conditions often are aggravated by chemical reactions with the contained compositions.
In situ vapor extraction methods which involve the placement of standpipes into the contaminated subsurface for removal of volatiles inherently result in non-uniform treatment with the greatest effectiveness being only within a relatively short distance from the standpipes.
Other methods which involve pumping and treatment of contaminated groundwater from an aquifer suffer from the problems of mass capital investment, high energy consumption and general inefficiency in treating the source of the problem, namely the contaminated soil.
It is therefore the primary object of the present invention to provide a cost effective and efficient apparatus for treatment of a hazardous waste site, whether it be a small gas station or a large multi-acre site.
In general, the solution to the problem involves a mobile apparatus comprising a trenching machine which is capable of operating to subsurface depths as low as 40 feet below the ground elevation and which effectively excavates, treats, and immediately recirculates treated soil back into the excavated trench in a rapid and continuous fashion.
Accordingly, the present invention provides a surface soil remediation apparatus comprising a mobile trenching machine, said trenching machine having a digging boom and moveable soil elevators for removing soil from a trench; a process conveyor on said apparatus for receiving excavated soil and for treating toxic contaminants in said soil; means on said apparatus for intimately mixing treatment reagents with said excavated soil in said process conveyor; and said process conveyor having a discharge end arranged for extruding treated soil from said process conveyor to refill said trench closely behind said digging boom.